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The term complicated pneumonia, in this chapter, will refer to pneumonia complicated by the accumulation of fluid or purulent material in the pleural space; this term includes parapneumonic effusions and empyema. The frequency of complicated pneumonia among all children with community-acquired pneumonia (CAP) is not known. However, complicated pneumonia has been reported to occur in 6–8% of children hospitalized with CAP.1,2

Streptococcus pneumoniae and Staphylococcus aureus remain the most common bacterial causes of complicated pneumonia (Table 34–1), though the epidemiology of complicated pneumonia appears to be changing. In February 2000, the Food and Drug Administration licensed a heptavalent pneumococcal conjugate vaccine (PCV7), which was subsequently recommended by the Advisory Committee on Immunization Practices and the American Academy of Pediatrics for use in children aged 2 years and younger as well as in older, high-risk children.3 Vaccine uptake was rapid and substantial declines in rates of invasive pneumococcal disease were documented in children.4 Randomized clinical trials5–7 and population-based observational studies1 suggested that PCV7 use has also decreased the incidence of CAP.

Postlicensure studies have revealed increases in nasopharyngeal carriage and invasive disease caused by pneumococcal serotypes not included in the currently licensed vaccine.8–10 It is not known whether the changing pneumococcal epidemiology will result in more or less frequent complications among patients with CAP. Investigators in Utah reported a regional increase in the frequency of empyema complicating CAP following PCV7 licensure; 86% of known isolates were pneumococcal serotypes not contained in PCV7.11 However, the results should be interpreted with caution because fewer than 10% of the isolates were available for serotyping.11 Furthermore, the investigators reported the absolute number of cases rather than population-based incidence rates.11 In contrast, adult studies suggest that pneumococcal vaccination reduces pneumonia-associated complication rates. In a large cohort of adults hospitalized with CAP, pneumococcal polysaccharide vaccine recipients were less likely to die of any cause and less likely to develop respiratory failure than individuals with CAP who did not receive the vaccine.12 Studies of more than 11,000 adults in Spain also found that pneumococcal vaccination reduced the risk of pneumococcal pneumonia (45% reduction), CAP-associated hospitalization, and mortality.13,14 Vaccination may reduce mortality and metastatic disease by preventing systemic dissemination of the organism during an episode of bacteremia. Whether PCV7 will lead to a similar decrease in adverse outcomes among children with CAP remains to be determined.